json

Documentation

Overview

Package json implements encoding and decoding of JSON objects as defined in RFC 4627.

Index

• func Compact(dst *bytes.Buffer, src []byte) os.Error
• func HTMLEscape(dst *bytes.Buffer, src []byte)
• func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) os.Error
• func Marshal(v interface{}) ([]byte, os.Error)
• func MarshalForHTML(v interface{}) ([]byte, os.Error)
• func MarshalIndent(v interface{}, prefix, indent string) ([]byte, os.Error)
• func Unmarshal(data []byte, v interface{}) os.Error
• type Decoder
  • func NewDecoder(r io.Reader) *Decoder
  • func (dec *Decoder) Decode(v interface{}) os.Error
• type Encoder
  • func NewEncoder(w io.Writer) *Encoder
  • func (enc *Encoder) Encode(v interface{}) os.Error
• type InvalidUTF8Error
  • func (e *InvalidUTF8Error) String() string
• type InvalidUnmarshalError
  • func (e *InvalidUnmarshalError) String() string
• type Marshaler
• type MarshalerError
  • func (e *MarshalerError) String() string
• type RawMessage
  • func (m *RawMessage) MarshalJSON() ([]byte, os.Error)
  • func (m *RawMessage) UnmarshalJSON(data []byte) os.Error
• type SyntaxError
  • func (e *SyntaxError) String() string
• type UnmarshalFieldError
  • func (e *UnmarshalFieldError) String() string
• type UnmarshalTypeError
  • func (e *UnmarshalTypeError) String() string
• type Unmarshaler
• type UnsupportedTypeError
  • func (e *UnsupportedTypeError) String() string

Functions

func Compact

func Compact(dst *bytes.Buffer, src []byte) os.Error

Compact appends to dst the JSON-encoded src with insignificant space characters elided.

func HTMLEscape

func HTMLEscape(dst *bytes.Buffer, src []byte)

HTMLEscape appends to dst the JSON-encoded src with <, >, and & characters inside string literals changed to \u003c, \u003e, \u0026 so that the JSON will be safe to embed inside HTML <script> tags. For historical reasons, web browsers don't honor standard HTML escaping within <script> tags, so an alternative JSON encoding must be used.

func Indent

func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) os.Error

Indent appends to dst an indented form of the JSON-encoded src. Each element in a JSON object or array begins on a new, indented line beginning with prefix followed by one or more copies of indent according to the indentation nesting. The data appended to dst has no trailing newline, to make it easier to embed inside other formatted JSON data.

func Marshal

func Marshal(v interface{}) ([]byte, os.Error)

Marshal returns the JSON encoding of v.

Marshal traverses the value v recursively. If an encountered value implements the Marshaler interface, Marshal calls its MarshalJSON method to produce JSON.

Otherwise, Marshal uses the following type-dependent default encodings:

Boolean values encode as JSON booleans.

Floating point and integer values encode as JSON numbers.

String values encode as JSON strings, with each invalid UTF-8 sequence replaced by the encoding of the Unicode replacement character U+FFFD.

Array and slice values encode as JSON arrays, except that []byte encodes as a base64-encoded string.

Struct values encode as JSON objects. Each exported struct field becomes a member of the object unless the field is empty and its tag specifies the "omitempty" option. The empty values are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero. The object's default key string is the struct field name but can be specified in the struct field's tag value. The "json" key in struct field's tag value is the key name, followed by an optional comma and options. Examples:

// Specifies that Field appears in JSON as key "myName"
Field int `json:"myName"`

// Specifies that Field appears in JSON as key "myName" and
// the field is omitted from the object if its value is empty,
// as defined above.
Field int `json:"myName,omitempty"`

// Field appears in JSON as key "Field" (the default), but
// the field is skipped if empty.
// Note the leading comma.
Field int `json:",omitempty"`

The key name will be used if it's a non-empty string consisting of only Unicode letters, digits, dollar signs, hyphens, and underscores.

Map values encode as JSON objects. The map's key type must be string; the object keys are used directly as map keys.

Pointer values encode as the value pointed to. A nil pointer encodes as the null JSON object.

Interface values encode as the value contained in the interface. A nil interface value encodes as the null JSON object.

Channel, complex, and function values cannot be encoded in JSON. Attempting to encode such a value causes Marshal to return an InvalidTypeError.

JSON cannot represent cyclic data structures and Marshal does not handle them. Passing cyclic structures to Marshal will result in an infinite recursion.

func MarshalForHTML

func MarshalForHTML(v interface{}) ([]byte, os.Error)

MarshalForHTML is like Marshal but applies HTMLEscape to the output.

func MarshalIndent

func MarshalIndent(v interface{}, prefix, indent string) ([]byte, os.Error)

MarshalIndent is like Marshal but applies Indent to format the output.

func Unmarshal

func Unmarshal(data []byte, v interface{}) os.Error

Unmarshal parses the JSON-encoded data and stores the result in the value pointed to by v.

Unmarshal traverses the value v recursively. If an encountered value implements the Unmarshaler interface, Unmarshal calls its UnmarshalJSON method with a well-formed JSON encoding.

Otherwise, Unmarshal uses the inverse of the encodings that Marshal uses, allocating maps, slices, and pointers as necessary, with the following additional rules:

To unmarshal a JSON value into a nil interface value, the type stored in the interface value is one of:

bool, for JSON booleans
float64, for JSON numbers
string, for JSON strings
[]interface{}, for JSON arrays
map[string]interface{}, for JSON objects
nil for JSON null

If a JSON value is not appropriate for a given target type, or if a JSON number overflows the target type, Unmarshal skips that field and completes the unmarshalling as best it can. If no more serious errors are encountered, Unmarshal returns an UnmarshalTypeError describing the earliest such error.

Types

type Decoder

type Decoder struct {
	// contains filtered or unexported fields
}

A Decoder reads and decodes JSON objects from an input stream.

func NewDecoder

func NewDecoder(r io.Reader) *Decoder

NewDecoder returns a new decoder that reads from r.

func (*Decoder) Decode

func (dec *Decoder) Decode(v interface{}) os.Error

Decode reads the next JSON-encoded value from its input and stores it in the value pointed to by v.

See the documentation for Unmarshal for details about the conversion of JSON into a Go value.

type Encoder

type Encoder struct {
	// contains filtered or unexported fields
}

An Encoder writes JSON objects to an output stream.

func NewEncoder

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new encoder that writes to w.

func (*Encoder) Encode

func (enc *Encoder) Encode(v interface{}) os.Error

Encode writes the JSON encoding of v to the connection.

See the documentation for Marshal for details about the conversion of Go values to JSON.

type InvalidUTF8Error

type InvalidUTF8Error struct {
	S string
}

func (*InvalidUTF8Error) String

func (e *InvalidUTF8Error) String() string

type InvalidUnmarshalError

type InvalidUnmarshalError struct {
	Type reflect.Type
}

An InvalidUnmarshalError describes an invalid argument passed to Unmarshal. (The argument to Unmarshal must be a non-nil pointer.)

func (*InvalidUnmarshalError) String

func (e *InvalidUnmarshalError) String() string

type Marshaler

type Marshaler interface {
	MarshalJSON() ([]byte, os.Error)
}

Marshaler is the interface implemented by objects that can marshal themselves into valid JSON.

type MarshalerError

type MarshalerError struct {
	Type  reflect.Type
	Error os.Error
}

func (*MarshalerError) String

func (e *MarshalerError) String() string

type RawMessage

type RawMessage []byte

RawMessage is a raw encoded JSON object. It implements Marshaler and Unmarshaler and can be used to delay JSON decoding or precompute a JSON encoding.

func (*RawMessage) MarshalJSON

func (m *RawMessage) MarshalJSON() ([]byte, os.Error)

MarshalJSON returns *m as the JSON encoding of m.

func (*RawMessage) UnmarshalJSON

func (m *RawMessage) UnmarshalJSON(data []byte) os.Error

UnmarshalJSON sets *m to a copy of data.

type SyntaxError

type SyntaxError struct {
	Offset int64 // error occurred after reading Offset bytes
	// contains filtered or unexported fields
}

A SyntaxError is a description of a JSON syntax error.

func (*SyntaxError) String

func (e *SyntaxError) String() string

type UnmarshalFieldError

type UnmarshalFieldError struct {
	Key   string
	Type  reflect.Type
	Field reflect.StructField
}

An UnmarshalFieldError describes a JSON object key that led to an unexported (and therefore unwritable) struct field.

func (*UnmarshalFieldError) String

func (e *UnmarshalFieldError) String() string

type UnmarshalTypeError

type UnmarshalTypeError struct {
	Value string       // description of JSON value - "bool", "array", "number -5"
	Type  reflect.Type // type of Go value it could not be assigned to
}

An UnmarshalTypeError describes a JSON value that was not appropriate for a value of a specific Go type.

func (*UnmarshalTypeError) String

func (e *UnmarshalTypeError) String() string

type Unmarshaler

type Unmarshaler interface {
	UnmarshalJSON([]byte) os.Error
}

Unmarshaler is the interface implemented by objects that can unmarshal a JSON description of themselves. The input can be assumed to be a valid JSON object encoding. UnmarshalJSON must copy the JSON data if it wishes to retain the data after returning.

type UnsupportedTypeError

type UnsupportedTypeError struct {
	Type reflect.Type
}

func (*UnsupportedTypeError) String

func (e *UnsupportedTypeError) String() string